Water systems are routinely monitored for the presence of pollutants, such as bacteria, viruses, pesticides, petroleum, acids, metals, and other chemicals. Increasingly, in recent years, pollution from prescription drugs and over-the-counter (OTC) medications has caused concern among water quality experts and environmental advocates. Pharmaceutical compounds have been detected in lakes, rivers, and streams, in amounts ranging from nanograms per liter to micrograms per liter. Even in small concentrations exposure to pharmaceutical pollutants has been shown to cause harm to aquatic ecosystems, such as, for example, altered sex ratios in certain fish populations. While the risk of low concentrations of pharmaceuticals in water appears to be minor for humans, sound information about the true effects and risks of chronic drug exposure due to pharmaceutical water pollution is lacking.
Pharmaceutical compounds that enter aquatic environments mainly come from human and veterinary medicines, such as antibiotics, antidepressants, blood thinners, hormones, and painkillers. Sometimes, unused or expired medications enter waterways as a result of improper disposal, for example, by flushing them down the toilet or drain. Pharmaceuticals can also enter water systems as a result of human and animal drug consumption. The body metabolizes only a fraction of most ingested drugs. The remainder is excreted through sweat, urine, or feces, which in turn ends up in wastewater systems. In the case of antibiotic- or hormone-fed livestock in large-scale feeding operations, these unmetabolized drug compounds can leach into groundwater from the tons of regularly produced manure. Furthermore, some medications are applied as creams or lotions rather than being ingested. The portions of these medications that are not absorbed into the skin are washed off into wastewater as well.
While there have been certain efforts to prevent improper disposal of pharmaceuticals, such as drug take-back programs and disposal guidelines from the federal Environmental Protection Agency (EPA), these efforts do not effectively capture all drugs that might be disposed of in water systems. Thus, wastewater treatment is an important measure to help remove those remaining pharmaceutical pollutants that do end up in the water.
There are multiple types of wastewater treatment. Activated sludge involves the use of air, bacteria, and/or protozoa to degrade organic materials and remove nutrients from sewage and industrial wastewaters. However, the efficiency of the activated sludge process in removing pollutants varies based on, for example, the temperature of degradation and hydraulic retention time for the various drug compounds. Additionally, activated sludge systems consume large amounts of energy. Also, construction, maintenance, and operation can be costly.
Other conventional systems include biological filtration, which is often utilized for municipal wastewater. These methods are insufficient to eliminate all persistent pharmaceutical residues, however, because of the diversity of drug properties. Additionally, sewage treatment results in the production of semi-solid waste byproducts, which require further treatment before being suitable for disposal.
Advanced processes such as UV, ozonation, microfiltration, and ultrasound can achieve degradation of drug compounds close to, or at 100%, efficiency. Nevertheless, these methods are inconsistent as well because of the complexity of pharmaceutical pollutants.
Given the increase in pharmaceutical and personal care product use, it is unclear whether these existing efforts will be sufficient to combat pharmaceutical water pollution, due to limitations such as cost, efficiency, secondary byproducts, and inconsistency.
Thus, further investigations into the removal and/or breakdown of widely used drugs in the environment, as well as improved methods of treating drug contamination in water sources, are warranted to prevent potential long-term consequences to the health of humans, other living organisms, and the environment.